提交 6c7f74f7 编写于 作者: A Artem Bityutskiy

UBIFS: use max_write_size for write-buffers

Switch write-buffers from 'c->min_io_size' to 'c->max_write_size' which
presumably has to be more write speed-efficient. However, when write-buffer
is synchronized, write only the the min. I/O units which contain the
data, do not write whole write-buffer. This is more space-efficient.

Additionally, this patch takes into account that the LEB might not start
from the max. write unit-aligned address.
Signed-off-by: NArtem Bityutskiy <Artem.Bityutskiy@nokia.com>
上级 3c89f396
......@@ -31,6 +31,26 @@
* buffer is full or when it is not used for some time (by timer). This is
* similar to the mechanism is used by JFFS2.
*
* UBIFS distinguishes between minimum write size (@c->min_io_size) and maximum
* write size (@c->max_write_size). The latter is the maximum amount of bytes
* the underlying flash is able to program at a time, and writing in
* @c->max_write_size units should presumably be faster. Obviously,
* @c->min_io_size <= @c->max_write_size. Write-buffers are of
* @c->max_write_size bytes in size for maximum performance. However, when a
* write-buffer is flushed, only the portion of it (aligned to @c->min_io_size
* boundary) which contains data is written, not the whole write-buffer,
* because this is more space-efficient.
*
* This optimization adds few complications to the code. Indeed, on the one
* hand, we want to write in optimal @c->max_write_size bytes chunks, which
* also means aligning writes at the @c->max_write_size bytes offsets. On the
* other hand, we do not want to waste space when synchronizing the write
* buffer, so during synchronization we writes in smaller chunks. And this makes
* the next write offset to be not aligned to @c->max_write_size bytes. So the
* have to make sure that the write-buffer offset (@wbuf->offs) becomes aligned
* to @c->max_write_size bytes again. We do this by temporarily shrinking
* write-buffer size (@wbuf->size).
*
* Write-buffers are defined by 'struct ubifs_wbuf' objects and protected by
* mutexes defined inside these objects. Since sometimes upper-level code
* has to lock the write-buffer (e.g. journal space reservation code), many
......@@ -46,8 +66,8 @@
* UBIFS uses padding when it pads to the next min. I/O unit. In this case it
* uses padding nodes or padding bytes, if the padding node does not fit.
*
* All UBIFS nodes are protected by CRC checksums and UBIFS checks all nodes
* every time they are read from the flash media.
* All UBIFS nodes are protected by CRC checksums and UBIFS checks CRC when
* they are read from the flash media.
*/
#include <linux/crc32.h>
......@@ -347,11 +367,17 @@ static void cancel_wbuf_timer_nolock(struct ubifs_wbuf *wbuf)
*
* This function synchronizes write-buffer @buf and returns zero in case of
* success or a negative error code in case of failure.
*
* Note, although write-buffers are of @c->max_write_size, this function does
* not necessarily writes all @c->max_write_size bytes to the flash. Instead,
* if the write-buffer is only partially filled with data, only the used part
* of the write-buffer (aligned on @c->min_io_size boundary) is synchronized.
* This way we waste less space.
*/
int ubifs_wbuf_sync_nolock(struct ubifs_wbuf *wbuf)
{
struct ubifs_info *c = wbuf->c;
int err, dirt;
int err, dirt, sync_len;
cancel_wbuf_timer_nolock(wbuf);
if (!wbuf->used || wbuf->lnum == -1)
......@@ -366,26 +392,48 @@ int ubifs_wbuf_sync_nolock(struct ubifs_wbuf *wbuf)
ubifs_assert(wbuf->size <= c->max_write_size);
ubifs_assert(wbuf->size % c->min_io_size == 0);
ubifs_assert(!c->ro_media && !c->ro_mount);
if (c->leb_size - wbuf->offs >= c->max_write_size)
ubifs_assert(!((wbuf->offs + wbuf->size) % c->max_write_size ));
if (c->ro_error)
return -EROFS;
ubifs_pad(c, wbuf->buf + wbuf->used, wbuf->avail);
/*
* Do not write whole write buffer but write only the minimum necessary
* amount of min. I/O units.
*/
sync_len = ALIGN(wbuf->used, c->min_io_size);
dirt = sync_len - wbuf->used;
if (dirt)
ubifs_pad(c, wbuf->buf + wbuf->used, dirt);
err = ubi_leb_write(c->ubi, wbuf->lnum, wbuf->buf, wbuf->offs,
wbuf->size, wbuf->dtype);
sync_len, wbuf->dtype);
if (err) {
ubifs_err("cannot write %d bytes to LEB %d:%d",
wbuf->size, wbuf->lnum, wbuf->offs);
sync_len, wbuf->lnum, wbuf->offs);
dbg_dump_stack();
return err;
}
dirt = wbuf->avail;
spin_lock(&wbuf->lock);
wbuf->offs += wbuf->size;
wbuf->avail = c->min_io_size;
wbuf->size = c->min_io_size;
wbuf->offs += sync_len;
/*
* Now @wbuf->offs is not necessarily aligned to @c->max_write_size.
* But our goal is to optimize writes and make sure we write in
* @c->max_write_size chunks and to @c->max_write_size-aligned offset.
* Thus, if @wbuf->offs is not aligned to @c->max_write_size now, make
* sure that @wbuf->offs + @wbuf->size is aligned to
* @c->max_write_size. This way we make sure that after next
* write-buffer flush we are again at the optimal offset (aligned to
* @c->max_write_size).
*/
if (c->leb_size - wbuf->offs < c->max_write_size)
wbuf->size = c->leb_size - wbuf->offs;
else if (wbuf->offs & (c->max_write_size - 1))
wbuf->size = ALIGN(wbuf->offs, c->max_write_size) - wbuf->offs;
else
wbuf->size = c->max_write_size;
wbuf->avail = wbuf->size;
wbuf->used = 0;
wbuf->next_ino = 0;
spin_unlock(&wbuf->lock);
......@@ -428,8 +476,13 @@ int ubifs_wbuf_seek_nolock(struct ubifs_wbuf *wbuf, int lnum, int offs,
spin_lock(&wbuf->lock);
wbuf->lnum = lnum;
wbuf->offs = offs;
wbuf->avail = c->min_io_size;
wbuf->size = c->min_io_size;
if (c->leb_size - wbuf->offs < c->max_write_size)
wbuf->size = c->leb_size - wbuf->offs;
else if (wbuf->offs & (c->max_write_size - 1))
wbuf->size = ALIGN(wbuf->offs, c->max_write_size) - wbuf->offs;
else
wbuf->size = c->max_write_size;
wbuf->avail = wbuf->size;
wbuf->used = 0;
spin_unlock(&wbuf->lock);
wbuf->dtype = dtype;
......@@ -509,8 +562,9 @@ int ubifs_bg_wbufs_sync(struct ubifs_info *c)
*
* This function writes data to flash via write-buffer @wbuf. This means that
* the last piece of the node won't reach the flash media immediately if it
* does not take whole minimal I/O unit. Instead, the node will sit in RAM
* until the write-buffer is synchronized (e.g., by timer).
* does not take whole max. write unit (@c->max_write_size). Instead, the node
* will sit in RAM until the write-buffer is synchronized (e.g., by timer, or
* because more data are appended to the write-buffer).
*
* This function returns zero in case of success and a negative error code in
* case of failure. If the node cannot be written because there is no more
......@@ -533,6 +587,8 @@ int ubifs_wbuf_write_nolock(struct ubifs_wbuf *wbuf, void *buf, int len)
ubifs_assert(wbuf->size % c->min_io_size == 0);
ubifs_assert(mutex_is_locked(&wbuf->io_mutex));
ubifs_assert(!c->ro_media && !c->ro_mount);
if (c->leb_size - wbuf->offs >= c->max_write_size)
ubifs_assert(!((wbuf->offs + wbuf->size) % c->max_write_size ));
if (c->leb_size - wbuf->offs - wbuf->used < aligned_len) {
err = -ENOSPC;
......@@ -561,9 +617,12 @@ int ubifs_wbuf_write_nolock(struct ubifs_wbuf *wbuf, void *buf, int len)
goto out;
spin_lock(&wbuf->lock);
wbuf->offs += c->min_io_size;
wbuf->avail = c->min_io_size;
wbuf->size = c->min_io_size;
wbuf->offs += wbuf->size;
if (c->leb_size - wbuf->offs >= c->max_write_size)
wbuf->size = c->max_write_size;
else
wbuf->size = c->leb_size - wbuf->offs;
wbuf->avail = wbuf->size;
wbuf->used = 0;
wbuf->next_ino = 0;
spin_unlock(&wbuf->lock);
......@@ -577,33 +636,57 @@ int ubifs_wbuf_write_nolock(struct ubifs_wbuf *wbuf, void *buf, int len)
goto exit;
}
/*
* The node is large enough and does not fit entirely within current
* minimal I/O unit. We have to fill and flush write-buffer and switch
* to the next min. I/O unit.
*/
dbg_io("flush jhead %s wbuf to LEB %d:%d",
dbg_jhead(wbuf->jhead), wbuf->lnum, wbuf->offs);
memcpy(wbuf->buf + wbuf->used, buf, wbuf->avail);
err = ubi_leb_write(c->ubi, wbuf->lnum, wbuf->buf, wbuf->offs,
wbuf->size, wbuf->dtype);
if (err)
goto out;
offs = wbuf->offs;
written = 0;
offs = wbuf->offs + wbuf->size;
len -= wbuf->avail;
aligned_len -= wbuf->avail;
written = wbuf->avail;
if (wbuf->used) {
/*
* The node is large enough and does not fit entirely within
* current available space. We have to fill and flush
* write-buffer and switch to the next max. write unit.
*/
dbg_io("flush jhead %s wbuf to LEB %d:%d",
dbg_jhead(wbuf->jhead), wbuf->lnum, wbuf->offs);
memcpy(wbuf->buf + wbuf->used, buf, wbuf->avail);
err = ubi_leb_write(c->ubi, wbuf->lnum, wbuf->buf, wbuf->offs,
wbuf->size, wbuf->dtype);
if (err)
goto out;
offs += wbuf->size;
len -= wbuf->avail;
aligned_len -= wbuf->avail;
written += wbuf->avail;
} else if (wbuf->offs & (c->max_write_size - 1)) {
/*
* The write-buffer offset is not aligned to
* @c->max_write_size and @wbuf->size is less than
* @c->max_write_size. Write @wbuf->size bytes to make sure the
* following writes are done in optimal @c->max_write_size
* chunks.
*/
dbg_io("write %d bytes to LEB %d:%d",
wbuf->size, wbuf->lnum, wbuf->offs);
err = ubi_leb_write(c->ubi, wbuf->lnum, buf, wbuf->offs,
wbuf->size, wbuf->dtype);
if (err)
goto out;
offs += wbuf->size;
len -= wbuf->size;
aligned_len -= wbuf->size;
written += wbuf->size;
}
/*
* The remaining data may take more whole min. I/O units, so write the
* remains multiple to min. I/O unit size directly to the flash media.
* The remaining data may take more whole max. write units, so write the
* remains multiple to max. write unit size directly to the flash media.
* We align node length to 8-byte boundary because we anyway flash wbuf
* if the remaining space is less than 8 bytes.
*/
n = aligned_len >> c->min_io_shift;
n = aligned_len >> c->max_write_shift;
if (n) {
n <<= c->min_io_shift;
n <<= c->max_write_shift;
dbg_io("write %d bytes to LEB %d:%d", n, wbuf->lnum, offs);
err = ubi_leb_write(c->ubi, wbuf->lnum, buf + written, offs, n,
wbuf->dtype);
......@@ -619,15 +702,18 @@ int ubifs_wbuf_write_nolock(struct ubifs_wbuf *wbuf, void *buf, int len)
if (aligned_len)
/*
* And now we have what's left and what does not take whole
* min. I/O unit, so write it to the write-buffer and we are
* max. write unit, so write it to the write-buffer and we are
* done.
*/
memcpy(wbuf->buf, buf + written, len);
wbuf->offs = offs;
if (c->leb_size - wbuf->offs >= c->max_write_size)
wbuf->size = c->max_write_size;
else
wbuf->size = c->leb_size - wbuf->offs;
wbuf->avail = wbuf->size - aligned_len;
wbuf->used = aligned_len;
wbuf->avail = c->min_io_size - aligned_len;
wbuf->size = c->min_io_size;
wbuf->next_ino = 0;
spin_unlock(&wbuf->lock);
......@@ -851,11 +937,11 @@ int ubifs_wbuf_init(struct ubifs_info *c, struct ubifs_wbuf *wbuf)
{
size_t size;
wbuf->buf = kmalloc(c->min_io_size, GFP_KERNEL);
wbuf->buf = kmalloc(c->max_write_size, GFP_KERNEL);
if (!wbuf->buf)
return -ENOMEM;
size = (c->min_io_size / UBIFS_CH_SZ + 1) * sizeof(ino_t);
size = (c->max_write_size / UBIFS_CH_SZ + 1) * sizeof(ino_t);
wbuf->inodes = kmalloc(size, GFP_KERNEL);
if (!wbuf->inodes) {
kfree(wbuf->buf);
......@@ -865,7 +951,14 @@ int ubifs_wbuf_init(struct ubifs_info *c, struct ubifs_wbuf *wbuf)
wbuf->used = 0;
wbuf->lnum = wbuf->offs = -1;
wbuf->avail = wbuf->size = c->min_io_size;
/*
* If the LEB starts at the max. write size aligned address, then
* write-buffer size has to be set to @c->max_write_size. Otherwise,
* set it to something smaller so that it ends at the closest max.
* write size boundary.
*/
size = c->max_write_size - (c->leb_start % c->max_write_size);
wbuf->avail = wbuf->size = size;
wbuf->dtype = UBI_UNKNOWN;
wbuf->sync_callback = NULL;
mutex_init(&wbuf->io_mutex);
......
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